Sudden food allergy

Mind Your Body of The Straits Times dated 2 June 2011, Thursday

Sudden food allergy

Food which you have been eating for years may suddenly produce an allergic reaction. Lea Wee reports
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Ms Ong Wei Ling carries an Epipen, which releases adrenaline, with her after developing an allergy to buckwheat six years ago.


Food-lover Ong Wei Ling, 30, was game when a friend asked her to sample soba (Japanese buckwheat noodles) in a restaurant six years ago.

But five minutes into the dish, the 30-year-old manager said her throat became dry and painful.
She said: 'My stomach started churning and I quickly went to the toilet and vomited.'

In the hospital, more than an hour later, her body started to itch and break out in hives.
She became breathless and the doctor gave her a shot of adrenaline, which improves breathing and brings up blood pressure.

She was found to be allergic to the buckwheat grain in soba.

Though food allergies are less common in adults than children, they can strike for the first time in adulthood.

Figures from the West show food allergies occur in one to two out of every 100 adults, compared to six to eight in every 100 infants, said Dr Cheng Yew Kuang, a consultant allergist and immunologist from Gleneagles Medical Centre.

People can carry on a food allergy from childhood or acquire one in their adult years. Unlike children, once adults have a food allergy, it tends to persist, said doctors here.

Most children outgrow their food allergies, with the exception of those who are allergic to peanuts, tree nuts or shellfish.

Dr Cheng cited a 2007 study here which showed that crustaceans, like shrimps and crabs, and molluscs, like the cone-shaped limpets, are the most common foods implicated in adult food allergies.

Adults tend to be allergic to a wider variety of food compared to children, said Dr Justina Tan, an associate consultant in rheumatology, allergy and immunology from Tan Tock Seng Hospital (TTSH).

This may simply be because they are exposed to more food, she said.

It also means a lot of detective work is needed to find out which food is causing the reaction.
Dr Tan said: 'Many ingredients can go into preparing a particular meal. If a person develops an allergic reaction after attending a 10-course wedding dinner, we may have to liaise with the hotel regarding each course that was served and find out what was put into each dish.'

She has patients who are allergic to dragonfruit and food baked or fried in dust mite-contaminated flour. One patient, who thought he was allergic to ang ku kueh (steamed glutinous rice flour cake), turned out to be reacting to the mung beans inside.

These types of food may not be included in the commercial extracts of the skin prick test, when a few drops of the purified allergen is introduced through a pin prick in the skin's surface to test for a reaction.

Said Dr Tan: 'Sometimes, we have to get our nurses to buy the problem food outside so that we can send it to the laboratory to make our own extract for a skin prick test.'

Adults can react to a food they are eating for the first time or they could react to a food they were previously tolerant of.

Polytechnic student Low Si Pei, 19, developed itching, swelling around her mouth and breathing difficulties after she ate fish during a Chinese New Year dinner with her relatives in Malaysia in February.

She said: 'As far as I can recall, I have been eating fish every day for years without any problem.'
She did not believe she was allergic to fish.

A few days later, she decided to sample some home-cooked tilapia. Again, she felt itching and swelling around her mouth and an 'uncomfortable feeling' in her throat.

It was only then that she decided to see a specialist, who confirmed she was indeed allergic to fish.

In food allergy, the immune system mistakes a particular food protein as harmful.
The first time the person eats the food, his immune system responds by creating immunoglobulin E (IgE) antibodies against it. The person is said to be sensitised but not yet allergic to the food protein.

He becomes allergic when subsequent encounters invoke the same reaction from his immune system, triggering the release of IgE antibodies and chemicals such as histamines.

This produces the classical symptoms of an allergy, such as hives, itching, nausea, diarrhoea or vomiting.

In a severe allergic reaction called anaphylaxis, the throat tightens and the blood pressure drops. The person can collapse or even die.

Nobody knows when a sensitised person will develop his first allergic symptoms, said Dr Tan.
Someone like Ms Low can be sensitised to fish as a child, but continue to eat fish with no problems throughout adolescence, only to suddenly develop an allergic reaction to it as an adult.
Dr Tan said people can also develop a reaction to a food they are eating for the first time if the food shares a similar protein to another food they are sensitised or allergic to.

In children, food allergies are often blamed on an immature immune system, which could explain why many subsequently outgrow their allergies as their immune system matures, said Dr Tan.
In adults, however, she said it is still unclear what causes this 'mature' immune system to change.

Some researchers blame it on genes while others say it is the environment.

One theory is that viruses in the environment could weaken the immune system, but this theory remains unproven.

Doctors do know, however, that adult food allergies share certain traits with childhood food allergies.

Both are more common in people who have another allergy, such as asthma, eczema or allergic rhinitis, said Dr Cheng.

And like childhood food allergies, adult food allergies can also cause severe anaphylactic reaction - a fact Ms Ong is well aware of.

She carries a self-injectable dose of adrenaline called an Epipen in her handbag wherever she goes.

But her allergy to buckwheat has not dampened her love for sampling different types of food, including, most recently, puffer fish.

She said: 'I will be fine so long as I avoid buckwheat.'